Xie Jialei, Winter Caitlyn, Winter Lauryn, Mateos Mariana
Department of Wildlife and Fisheries Sciences, Texas A&M University, College Station, TX 77843-2258, USA.
Department of Wildlife and Fisheries Sciences, Texas A&M University, College Station, TX 77843-2258, USA
FEMS Microbiol Ecol. 2015 Feb;91(2):1-11. doi: 10.1093/femsec/fiu017. Epub 2014 Dec 10.
Maternally transmitted endosymbionts of insects are ubiquitous in nature and play diverse roles in the ecology and evolution of their hosts. To persist in host lineages, many symbionts manipulate host reproduction to their advantage (e.g. cytoplasmic incompatibility and male-killing), or confer fitness benefits to their hosts (e.g. metabolic provisioning and defense against natural enemies). Recent studies suggest that strains of the bacterial genus Spiroplasma protect their host (flies in the genus Drosophila) against parasitoid attack. The Spiroplasma-conferred protection is partial and flies surviving a wasp attack have reduced adult longevity and fecundity. Therefore, it is unclear whether protection against wasps alone can counter Spiroplasma loss by imperfect maternal transmission and any possible fitness costs to harboring Spiroplasma. To address this question, we conducted a population cage study comparing Spiroplasma frequencies over time (host generations) under conditions of high wasp pressure and no wasp pressure. A dramatic increase of Spiroplasma prevalence was observed under high wasp pressure. In contrast, Spiroplasma prevalence in the absence of wasps did not change significantly over time; a pattern consistent with random drift. Thus, the defensive mechanism may contribute to the high prevalence of Spiroplasma in host populations despite imperfect vertical transmission.
昆虫母体传播的内共生菌在自然界中普遍存在，并在其宿主的生态和进化中发挥着多样的作用。为了在宿主谱系中持续存在，许多共生菌会操纵宿主繁殖以使其自身受益（例如细胞质不亲和和雄性致死），或者为宿主提供适应性益处（例如代谢供应和抵御天敌）。最近的研究表明，螺旋体属细菌菌株能保护其宿主（果蝇属的果蝇）免受寄生蜂攻击。螺旋体提供的保护是不完全的，在黄蜂攻击中存活下来的果蝇成虫寿命和繁殖力会降低。因此，尚不清楚仅针对黄蜂的保护能否抵消因母体传播不完善导致的螺旋体损失以及携带螺旋体可能产生的任何适应性成本。为了解决这个问题，我们进行了一项种群笼养研究，比较了在高黄蜂压力和无黄蜂压力条件下，随着时间推移（宿主代数）螺旋体的频率。在高黄蜂压力下观察到螺旋体流行率急剧上升。相比之下，在没有黄蜂的情况下，螺旋体流行率随时间没有显著变化；这一模式与随机漂变一致。因此，尽管垂直传播不完善，但这种防御机制可能有助于螺旋体在宿主种群中的高流行率。
